/Engine/Source/Runtime/RHI/Public/RHIResources.h
E.g. for a a full 256 x 256 area starting at (0, 0) it would be the values would be 0, 0, 256, 256
FResolveRect ( int32 InX1, int32 InY1, int32 InX2, int32 InY2 )